Heretofore, mobile communication systems have been defined in which an inter-frequency handover can be performed for a mobile station UE in a communication environment including multiple cells (frequency cells) which uses different frequencies.
Specifically, in a mobile communication system based on the “LTE (Long Term Evolution)” defined by the 3GPP, the mobile station UE measures the communication quality in a cell (inter-frequency cell) adjacent to a frequency cell currently used for communication. Then, when determining that the measured communication quality satisfies a certain communication quality by referring to a determination condition, the mobile station UE transmits a measurement report indicating the determination, to a radio base station eNB. According to the received measurement report, the radio base station eNB determines that an inter-frequency handover from the frequency cell currently used for communication to another frequency cell having a better communication quality is to be performed for the mobile station UE.
Here, the LTE mobile communication system needs to coexist with other mobile communication systems such as a UTRAN (UMTS Terrestrial Radio Access Network) mobile communication system and a GERAN (GSM EDGE Radio Access Network) mobile communication system, which have already been introduced, and to support mobility between itself and these mobile communication systems.
Since different mobile communication systems have different services, transmission rates, radio efficiencies and the like to be provided, the optimal mobile communication system is different depending on the contract terms and the service type of a user.
Moreover, if the LTE mobile communication system includes LTE carriers (frequencies) having different bandwidths in order to support various bandwidths from 1.4 MHz to 20 MHz, the optimal frequencies are different among the services.
For example, a wide-bandwidth carrier (frequency) is preferably used for a service for downloading a large amount of data instantaneously. By contrast, such a wide-bandwidth carrier (frequency) is not necessarily used for a service such as a voice service, or a service for communication between machines.
Furthermore, flexible switching of mobile communication systems (RATs) and flexible switching of carriers (frequencies) are desired to be performed according to congestion degrees of the RATs and the frequencies.
This requires a method capable of flexibly switching between RATs and between frequencies, and particularly a control method capable of designating priorities for RATs and for frequencies, according to the contract terms and the service type of a user, and congestion degrees.
However, the conventional mobile communication systems have had a problem of being unable to flexibly change the above-described determination condition between multiple communication systems (RAT) or between carriers (frequencies) according to the priority of multiple mobile communication systems (RAT) or of carriers (frequencies).
The present invention has been made in view of the above-described problem, and has an object of providing a mobile communication method and a radio base station that are capable of flexibly changing a determination condition for determining whether or not a mobile station UE is to transmit a measurement report.
A first aspect of the present invention is summarized as a mobile communication method including the steps of: transmitting, from a radio base station to a mobile station, a measurement rule designation command which designates addition or deletion of a measurement rule; transmitting, from the radio base station to the mobile station, a measurement object designation command, which designates addition or deletion of a measurement object, independently from the measurement rule designation command; transmitting, from the radio base station to the mobile station, a mapping designation command which designates associating of the measurement object with the measurement rule; storing, at the mobile station, the measurement rule and the measurement object in association with each other, according to the mapping designation command; measuring, at the mobile station, a communication quality of an inter-frequency cell of a frequency defined by the stored measurement object; and transmitting, from the mobile station to the radio base station, a measurement report, when determining that a determination condition defined by the measurement rule associated with the measurement object is satisfied, on the basis of a measurement result of the communication quality.
In the first aspect, the radio base station can transmit the measurement rule designation command, the measurement object designation command and the mapping designation command by the same signaling.
In the first aspect, the mobile communication method can further include the step of: deleting, at the mobile station, the association between the measurement rule and the measurement object, based on the mapping designation command.
In the first aspect, the measuring of the communication quality can include: a first measurement for measuring a communication quality of an inter-frequency cell of a frequency having a higher priority than that of a cell currently used for communication; a second measurement for measuring a communication quality of an inter-frequency cell of a frequency having the same priority as that of the cell currently used for communication; and a third measurement for measuring a communication quality of an inter-frequency cell of a frequency having a lower priority than that of the cell currently used for communication.
In the first aspect, a first determination condition, a second determination condition and a third determination condition can be different; the first determination condition can be used for determining whether or not a measurement report is to be transmitted on the basis of the communication quality measured by the first measurement; the second determination condition can be used for determining whether or not a measurement report is to be transmitted on the basis of the communication quality measured by the second measurement; and the third determination condition can be used for determining whether or not a measurement report is to be transmitted on the basis of the communication quality measured by the third measurement.
A second aspect of the present invention is summarized as a radio base station including: a measurement rule designation command transmitter unit configured to transmit, to a mobile station, a measurement rule designation command which designates addition or deletion of a measurement rule; a measurement object designation command transmitter unit configured to transmit, to the mobile station, a measurement object designation command, which designates addition or deletion of a measurement object, independently from the measurement rule designation command; and a mapping designation command transmitter unit configured to transmit, to the mobile station, a mapping designation command which designates associating of the measurement object with the measurement rule, wherein the mobile station measures a communication quality of an inter-frequency cell of a frequency defined by the measurement object stored in the mobile station, and the mobile station transmits a measurement report to the radio base station, when determining that a determination condition defined by the measurement rule associated with the measurement object is satisfied, on the basis of a measurement result of the communication quality.
In the second aspect, the measurement object designation command transmitter unit and the mapping designation command transmitter unit can be configured to transmit the measurement rule designation command, the measurement object designation command and the mapping designation command by the same signaling.
In the second aspect, the measuring of the communication quality can include: a first measurement for measuring a communication quality of an inter-frequency cell of a frequency having a higher priority than that of a cell currently used for communication; a second measurement for measuring a communication quality of an inter-frequency cell of a frequency having the same priority as that of the cell currently used for communication; and a third measurement for measuring a communication quality of an inter-frequency cell of a frequency having a lower priority than that of the cell currently used for communication.
In the second aspect, a first determination condition, a second determination condition and a third determination condition can be different; the first determination condition can be used for determining whether or not a measurement report is to be transmitted on the basis of the communication quality measured by the first measurement; the second determination condition can be used for determining whether or not a measurement report is to be transmitted on the basis of the communication quality measured by the second measurement; and the third determination condition can be used for determining whether or not a measurement report is to be transmitted on the basis of the communication quality measured by the third measurement.